Copper alloy

ABSTRACT

A method of producing a copper alloy containing: Ni and/or Si and at least one or more of B, Al, As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co, and Be, the copper alloy having a precipitate X composed of Ni and Si, and a precipitate Y composed of Ni and/or Si, and at least one or more of B, Al, As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co, and Be, in which a grain diameter of the precipitate Y is 0.01 to 2 μm.

CROSS-REFERENCE TO RELATED CASES

This application is a divisional of U.S. application Ser. No.11/846,074, filed on Aug. 28, 2007, which was a continuation applicationof International Application No. PCT/JP2006/303738, filed on Feb. 28,2006, which was based on and claims priority under 35 U.S.C. §119(a) ofJapanese Application Nos. 2005-055144 filed on Feb. 28, 2005 and2005-055147 filed on Feb. 28, 2005, both of which being incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a method of producing copper alloyapplicable as materials for electric and electronic instruments.

BACKGROUND ART

Heretofore, generally, in addition to iron-based materials, copper-basedmaterials, such as phosphor bronze, red brass, and brass, which areexcellent in electrical conductivity and thermal conductivity, have beenused widely as materials for electric and electronic instruments(electrical and electronic machinery and tools).

Recently, demands for miniaturization, weight saving, and associatedhigh-density packaging of parts of electric and electronic instrumentshave increased, and various characteristics of higher levels arerequired for the copper-based materials applied thereto. Examples ofbasic characteristics required include mechanical properties, electricalconductivity, stress relaxation resistance, bending property, and springproperty. Of those, improvements in stress relaxation resistance,tensile strength, and bending property are strongly required, forsatisfying the recent demands for the miniaturization of parts orcomponents for the products described above. In particular, forminiaturizing electronic parts, for example, tensile strength andbending property are necessary for lead frame materials, while stressrelaxation resistance as well as tensile strength is necessary forconnectors and terminal materials.

The requirements for those materials differ form each other little bylittle, depending on uses, kinds, shapes, or the like of the parts, andspecific requirements include: a tensile strength of 700 MPa or more anda bending property of R/t≦1.0 (in which R represents a bending radius,and t represents a sheet thickness), or a tensile strength of 800 MPa ormore and a bending property of R/t≦2.0; more preferably a tensilestrength of 800 MPa or more and a bending property of R/t<1.5, or atensile strength of 900 MPa or more and a bending property of R/t<2.0.

Thinning of the material is inevitable in association withminiaturization of the parts. Accordingly, conventional copper alloysare not always durable to long term uses due to increased stress loadedon the material and increased temperatures of working environments.Under these situations, more improved stress relaxation resistance isdesired. Minimum stress relaxation resistance is a value defined by theStandard of the Electronic Materials Manufacturers Association of Japan(EMAS-3003), wherein the copper alloy material is desired to satisfy astress relaxation ratio of less than 20% at a temperature condition of150° C.

The required characteristics have reached a level that cannot besatisfied with conventional commercially available, mass-producedalloys, such as phosphor bronze, red brass, and brass. Thus,conventionally, such alloys each have an increased strength by: allowingSn or Zn having a very different atomic radius from that of copper as amatrix phase, to be contained as a solid solution in Cu; and subjectingthe resultant alloy having the solid solution to cold-working such asrolling or drawing. The method can provide high-strength materials byemploying a large cold-working ratio, but employment of a largecold-working ratio (generally 50% or more) is known to conspicuouslydegrade bending property of the resultant alloy material. The methodgenerally involves a combination of solid solution strengthening andworking strengthening.

An alternative strengthening method is a precipitation strengtheningmethod (a precipitation hardening method) that involves formation of aprecipitate of a nanometer order in the materials. The precipitationstrengthening method has merits of increasing strength and improvingelectrical conductivity at the same time, and is used for many alloys.

Of those, a strengthened alloy prepared by forming a precipitatecomposed of Ni and Si by adding Ni and Si into Cu, so-called a Corsonalloy, has a remarkably high strengthening ability compared with manyother precipitation-type alloys. This strengthening method is also usedfor some commercially available alloys (e.g. CDA70250, a registeredalloy of Copper Development Association (CDA)). When the alloy generallysubjected to precipitating strengthening is used for terminal/connectormaterials, the alloy is produced through a production processincorporating the following two important heat treatments. One is a heattreatment which involves heat treatment at a high temperature (generally700° C. or higher) near a melting point, so-called solution treatment,to allow Ni and Si precipitated through casting or hot-rolling to becontained as a solid solution into a Cu matrix. The other is a heattreatment which involves heat treatment at a lower temperature than thatof the solution treatment, so-called aging treatment, to precipitate Niand Si, which are in the solid solution caused at the high temperature,as a precipitate. The strengthening method utilizes a difference inconcentrations of Ni and Si entering Cu as a solid solution at hightemperatures and low temperatures.

An example of the Corson alloy applicable for electric and electronicinstruments includes an alloy having a defined grain size of precipitate(see, for example, Patent Document 1). However, the precipitation-typealloy has such problems that the crystal grain size increases to causegiant crystal grains upon the solution treatment, and that the crystalgrain size upon the solution treatment remains unchanged and becomes thecrystal grain size of a product since the aging treatment generally doesnot involve recrystallization. An increased amount of Ni or Si to beadded requires a solution treatment at a higher temperature, and itresults in that the crystal grain size tends to increase to cause giantcrystal grains, through a heat treatment in a short period of time. Theresultant giant crystal grains occurred in this way cause problems ofconspicuous deterioration in bending property.

Alternatively, a method of improving the bending property of a copperalloy involves addition of Mn, Ni, and P for a mutual reaction toprecipitate a compound, without use of a Ni—Si precipitate (see, forexample, Patent Document 2). However, the resultant alloy has a tensilestrength of about 640 MPa at most, which is not sufficient forsatisfying the recent demands for high strength through miniaturizationof parts. Addition of Si to the copper alloy decreases the amount of theNi—P precipitate, to thereby reduce the mechanical strength andelectrical conductivity. Further, excess Si and P cause problems ofoccurrence of crack upon hot working.

As is apparent from the above, the bending property is hardly maintainedwith increasing tensile strength. Accordingly, it is desired to developthe copper alloy allowing tensile strength, bending property, electricalconductivity, and stress relaxation resistance to be compatible at highlevels to one another or keeping a good balance among them, while theseproperties are able to be controlled depending on the uses.

Other and further features and advantages of the present invention willappear more fully from the following description.

Patent Document 1: JP-A-11-43731 (“JP-A” means unexamined publishedJapanese patent application)

Patent Document 2: JP-A-2003-82425

DISCLOSURE OF INVENTION

For solving the above-mentioned problems, the present inventioncontemplates providing a copper alloy having high bending property andexcellent tensile strength, electrical conductivity and stressrelaxation resistance, wherein characteristics of the copper alloy maybe readily balanced depending on uses, and the copper alloy is favorablefor materials of lead frames, connectors, terminals or the like ofelectric and electronic instruments, particularly for materials ofvehicle connectors, terminals, relays and switches or the like.

The inventors of the present invention have conducted intensive studieson a copper alloy suitably used for electrical and electronic parts, andhave noticed the relations between characteristics of the alloy andgrain diameters of Ni—Si precipitates and other precipitates in a copperalloy structure, and between the proportions of the distribution densityof the precipitates and suppression of coarsening of crystal grains. Asa result, the inventors have completed, through intensive studies, thecopper alloy of the present invention that is able to form a materialhaving excellent tensile strength and being excellent in bendingproperty, electrical conductivity, and stress relaxation resistance.

According to the present invention, there is provided the followingmeans:

(1) A copper alloy, having: a precipitate Y composed of Ni and/or Si,and at least one or more selected from the group consisting of B, Al,As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal(MM), Co, and Be; and a precipitate X composed of Ni and Si, wherein agrain diameter of the precipitate Y is 0.01 to 2 μm;

(2) The copper alloy, wherein the grain diameter of the precipitate Y is0.02 to 0.9 μm;

(3) A copper alloy, having: a precipitate X composed of Ni and Si; andat least one precipitate selected from the group consisting of aprecipitate Y1 composed of Ni, Si, and Cr, a precipitate Y2 composed ofNi, Si, and Co, a precipitate Y3 composed of Ni, Si, and Zr, and aprecipitate Z composed of Ni, Si, and B, wherein a grain diameter of theat least one precipitate selected from the group consisting of theprecipitates Y1, Y2, Y3, and Z is 0.1 to 2 μm;

(4) A copper alloy, comprising: N±2.0 to 5.0 mass %, S±0.3 to 1.5 mass%, at least one or more selected from the group consisting of B, Al, As,Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM),Co, and Be each in an amount of 0.005 to 1.0 mass %, with a balancebeing Cu and inevitable impurities; said copper alloy having aprecipitate X composed of Ni and Si; and a precipitate Y composed of Ni,Si, and at least one or more selected from the group consisting of B,Al, As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Mischmetal (MM), Co, and Be, wherein a grain diameter of the precipitate Y is0.01 to 2 μm;

(5) A copper alloy, comprising: N±2.0 to 5.0 mass %, S±0.3 to 1.5 mass%, at least one or more selected from the group consisting of B, Al, As,Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM),Co, and Be each in an amount of 0.005 to 1.0 mass %, with a balancebeing Cu and inevitable impurities; said copper alloy having aprecipitate X composed of Ni and Si; and a precipitate Y composed of Nior Si, and at least two or more selected from the group consisting of B,Al, As, Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Mischmetal (MM), Co, and Be, wherein a grain diameter of the precipitate Y is0.01 to 2 μm;

(6) A copper alloy, comprising: N±2.0 to 5.0 mass %, S±0.3 to 1.5 mass%, at least one or more selected from the group consisting of B, Al, As,Hf, Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM),Co, and Be each in an amount of 0.005 to 1.0 mass %, with a balancebeing Cu and inevitable impurities; said copper alloy having aprecipitate X composed of Ni and Si; and a precipitate Y composed of atleast three or more selected from the group consisting of B, Al, As, Hf,Zr, Cr, Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co,and Be, wherein a grain diameter of the precipitate Y is 0.01 to 2 μm;

(7) The copper alloy according to any one of Claims (1) to (6), whereinthe melting point of the precipitate Y is higher than a solid solutiontreatment temperature;

(8) The copper alloy according to any one of (1) to (7), wherein thenumber of precipitates X per mm² is 20 to 2,000 times the number ofprecipitates Y per mm²;

(9) The copper alloy according to any one of Claims (1) to (8), whereinthe number of precipitates X is 10⁸ to 10¹² per mm², and the number ofprecipitates Y is 10⁴ to 10⁸ per mm²;

(10) The copper alloy according to any one of Claims (1) to (9), whereina composition of the copper alloy further comprises at least one or moreselected from Sn 0.1 to 1.0 mass %, Zn 0.1 to 1.0 mass %, and Mg 0.05 to0.5 mass %;

(11) The copper alloy according to any one of (1) to (10), which has astress relaxation ratio of less than 20%; and

(12) The copper alloy according to any one of (1) to (11), which is foruse as a material of an electric or electronic instrument.

The copper alloy of the present invention compatibly has a tensilestrength and a bending property (R/t) at high levels, without impairingelectrical conductivity, while stress relaxation resistance that maylargely affect reliability of connectors and terminals is furtherimproved. The copper alloy of the present invention is excellent inbending property and stress relaxation resistance, as compared withconventional copper alloys having the same level of tensile strength.The copper alloy of the present invention is a copper alloy favorablefor use in electric and electronic instruments that are required forhigher characteristics upon miniaturization. In addition to the above,the copper alloy of the present invention is excellent in otherproperties such as spring property.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferable embodiments of the copper alloy of the present invention willbe described in detail.

The copper alloy of the present invention is an inexpensive,high-performance copper alloy maintaining high electrical conductivity,having excellent bending property and other favorable properties, and itis preferable for a variety of electric and electronic instrumentsincluding electronic parts, e.g. vehicle terminals/connectors, relays,and switches.

Preferable embodiments of the copper alloy of the present invention willbe described in detail.

The present invention relates to controlling of a grain size of aprecipitate of a copper alloy. To be specific, a method of controlling agrain size has been realized from two standpoints.

First, the method of controlling a grain size can be realized by usingan element that does not allow a crystal grain size to increase to causegiant grains upon a solution treatment. Each of precipitates composed ofNi, Si and α; Ni, a and β; Si, α and β; and α, β and γ (herein α, β andγ each are an element other than Ni and Si) does not form any solidsolution in a Cu matrix phase even at high temperatures of the solutiontreatment, and that the precipitate exists in crystal grains of the Cumatrix phase and the precipitate grains, to exhibit an action and effectof suppressing growth of the crystal grains of the matrix.

Second, the method of controlling a grain size can be realized by usingan element that serves as a nucleus at initial recrystallization uponthe solution treatment. An intermetallic compound which is a precipitatecomposed of Ni, Si and α; Ni, α and β; Si, α and β; and α, β and γ(herein α, β and γ each are an element other than Ni and Si) serves as anucleation site for recrystallization at a solution treatmenttemperature, and that more crystal grains are formed (nucleation) thanthat in the case where the precipitate is not added. Formation of morecrystal grains causes mutual interference of the crystal grains duringgrain growth, to thereby suppress the grain growth. Multi-componentprecipitates are preferable for the action and effect of the nucleationsite for recrystallization.

In the present invention, the term “precipitate” means to includeintermetallic compounds, carbides, oxides, sulfides, nitride, compounds(solid solutions), and element metals.

The aforementioned precipitate is not to form any solid solution in theCu matrix even during the solution treatment. That is, the precipitatemust have a melting point higher than the solution treatmenttemperature. The precipitate is not limited to the aforementionedprecipitates as long as it has a melting point higher than the solutiontreatment temperature. Further, the precipitate is not limited as longas it provides an effect of preventing growth of too large crystalgrains during the solution treatment or forming many crystal grains(nucleation) by serving as a nucleation site for recrystallization.

The copper alloy of the present invention is an inexpensive,high-performance copper alloy maintaining high electrical conductivity,having excellent bending property and other favorable properties, and itis preferable for a variety of electric and electronic instrumentsincluding electronic parts, e.g. vehicle terminals/connectors, relays,and switches.

Next, an alloy structure of the copper alloy of the present inventionwill be described.

The grain diameter of the precipitate X composed of Ni and Si ispreferably 0.001 to 0.1 μm, more preferably from 0.003 to 0.05 μm, andfurther preferably 0.005 to 0.02 μm. The strength is not improved whenthe grain diameter is too small, while the bending property decreaseswhen the grain diameter is too large.

The precipitate Y composed of Ni and/or Si and at least one or moreselected from the group consisting of B, Al, As, Hf, Zr, Cr, Ti, C, Fe,P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co and Be; theprecipitate Y1 composed of Ni, Si and Cr; the precipitate Y2 composed ofNi, Si and Co; and the precipitate Y3 composed of Ni, Si and Zr eachhave larger effects for fining crystal grains than Ni—Si precipitate Xdoes, during the solid solution treatment as a heat treatment at hightemperatures. Those effects become particularly large by the precipitateY1 and the precipitate Y2.

This effect acts for improving bending property. Since solid solutiontreatment can be applied at higher temperatures than temperatures of theconventional solid solution treatment, this effect can contribute toimprovements of the tensile strength and the stress relaxationresistance by increasing the amount of the solid solution in the copperalloy as well as the amount of precipitates during aging treatments.This effect is particularly enhanced when the melting point ofprecipitate Y is higher than the melting point of precipitate X. Themelting point of precipitate X is preferably from 650 to 1,050° C., andthe melting point of precipitate Y is preferably higher than the meltingpoint of precipitate X and 1,100° C. or less.

The grain diameter of precipitate Y is preferably 0.01 to 2.0 μm, morepreferably 0.05 to 0.5 μm, and most preferably from 0.05 to 0.13 μm.This is because an effect for suppressing growth of crystal grains andan effect for increasing the number of nucleation sites are notexhibited when the grain diameter is too small, while the bendingproperty decreases when the grain diameter is too large. In the presentinvention, the grain diameter of precipitate Y is preferably larger thanthe grain diameter of precipitate X. The ratio of the grain diametersbetween Y and X (Y/X) preferably exceeds 1 and 2,000 or less, morepreferably 5 to 500.

Next, the action and effect of each alloy element and a range ofaddition amount of the alloy element will be described.

Ni and Si are elements that can be added in a controlled addition ratioof Ni to Si for forming a Ni—Si precipitate for precipitationstrengthening, to thereby enhance the mechanical strength of the copperalloy. The amount of Ni to be added is generally 2.0 to 5.0 mass %,preferably 2.1 to 4.6 mass %. The Ni amount is more preferably 3.5 to4.6 mass %, for satisfying a tensile strength of 800 MPa or more and abending property of R/t<1.5, or a tensile strength of 900 MPa or moreand a bending property of R/t<2. A too small Ni amount provides a smallprecipitated and hardened amount that results in insufficient mechanicalstrength, and a too large Ni amount results in a conspicuously lowelectrical conductivity.

Further, the ratio of the addition amount of Ni to Si of about 1 to 4(i.e. the amount of Ni to be added being 4 vs. that of Si being about 1)in terms of mass ratio, is known to provide the largest strengtheningeffect. When the Si addition amount exceeds 1.5 mass %, it is apt tocause cracking of an ingot of the copper alloy during hot working. Thus,the Si addition amount is generally 0.3 to 1.5 mass %, preferably 0.5 to1.1 mass %, more preferably 0.8 to 1.1 mass %. B, Al, As, Hf, Zr, Cr,Ti, C, Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co, and Beform precipitate Y by themselves or in combination with Ni and/or Si.While precipitate Y serves for suppressing crystal grains fromcoarsening during the solid solution treatment as described above, it isnot responsible for or does not largely contribute to precipitationstrengthening. The content of each of the above-mentioned elements isgenerally 0.005 to 1.0 mass %, preferably 0.007 to 0.5 mass %, and morepreferably 0.01 to 0.1 mass %. The quality of an ingot is impaired byforming large crystals during melt-casting when the amount of additionof these elements is too large, while attainment of desired effects isimpossible when the amount is too small.

Further, in particularly, Cr, Co and Zr form precipitates in combinationwith main components, Ni and Si. While the effect is to suppress crystalgrains from being coarsened during the solid solution treatment, tothereby control the crystal grain diameter as described above, it doesnot largely contribute to precipitation strengthening. The amount ofaddition of these elements is preferably 0.005 to 1.0 mass %, morepreferably 0.1 to 0.3 mass % for permitting the effect to be exhibited.The quality of the ingot may be impaired by forming large crystalsduring melt-casting when the amount of addition of these elements is toolarge, while the effect of addition is not exhibited when the amount istoo small.

B forms a precipitate with main constituents Ni and Si. The effect of Bas the same manner as the above Cr, Co or Zr is that B is an element forsuppressing increase of the crystal grain size to become too large(giant) during the solution treatment, but B takes no part in theprecipitation strengthening. The B addition amount is preferably 0.005to 0.1 mass %, more preferably 0.01 to 0.07 mass %, for exhibiting theeffect. A too large B addition amount results in too large crystallizedproduct during melt-casting to cause problems in ingot quality, and atoo small B addition amount provides no addition effect.

Further, Zn, Sn, and/or Mg are preferably added to further improve thecharacteristics.

Zn is an element which forms a solid solution in a matrix, but Znaddition significantly alleviates solder embrittlement. Thus, Zn isadded preferably in an amount of 0.1 to 1.0 mass %. The preferableprimary uses of the alloy of the present invention are electric andelectronic instruments and electronic part terminal materials such asvehicle terminals/connectors, relays, and switches. Most of them arejoined by solder, and thus the enhancement of reliability in the joinedportions is one of the important elemental techniques.

Further, Zn addition may lower the melting point of the alloy, tocontrol the states of formation of the precipitate composed of Ni and Band the precipitate composed of Mn and P. Both the precipitates areformed during solidification. Thus, a high solidification temperature ofthe alloy increases the grain size, to provide a small contribution ofthe precipitates to the effects of suppressing increase of the crystalgrain size and forming a nucleation site for the crystal grains. Thelower limit of Zn addition is defined as 0.1 mass %, because it is aminimum necessary amount that provides alleviations in solderembrittlement. The upper limit of Zn addition is defined as 1.0 mass %,because a Zn addition amount more than 1.0 mass % may degrade theelectrical conductivity.

Sn and Mg to be added are also preferable elements for their uses. Snand Mg addition provides an effect of improving creep resistance, whichis emphasized in electronic instrument terminals/connectors. The effectis also referred to as stress relaxing resistance, and it is animportant characteristic that assumes reliability of theterminals/connectors. Solely addition of Sn or Mg may improve the creepresistance, but the use in combination of Sn and Mg can further improvethe creep resistance by a synergetic effect. The lower limit of Snaddition is defined as 0.1 mass %, because it is a minimum necessaryamount that provides improvements in creep resistance. The upper limitof Sn addition is defined as 1 mass %, because a Sn addition amount morethan 1 mass % may degrade the electrical conductivity. The lower limitof Mg addition is defined as 0.05 mass %, because an addition amount ofMg less than 0.05 mass % provides no effect of improving the creepresistance. The upper limit of Mg addition is defined as 0.5 mass %,because an Mg addition amount of more than 0.5 mass % not only saturatesthe effect. Further, when an Mg addition amount is more than 0.5 mass %,it may degrade hot-workability at a particularly-high temperature,depending on the composition of the alloy.

Sn and Mg have a function of accelerating formation of a precipitatecomposed of Ni and Si. It is important to add preferable amounts ofthese Sn and Mg, serving as fine nucleation sites for the precipitate.

Next, the relationship between the number of precipitate X (the numberof grains of the precipitate X) and the number of precipitate Y asanother precipitate will be described below.

The number of precipitate X per mm² on an arbitrary cross section in thecopper alloy is preferably 20 to 2,000 times the number of correspondingprecipitate Y per mm². This is because the bending property isparticularly enhanced among the characteristics, and a sufficientmechanical strength can be obtained. The number of the precipitate X ismore preferably 100 to 1,500 times the number of the precipitate Y.

Specifically, the number of precipitates X is preferably 10⁸ to 10¹² permm², and the number of precipitates Y that correspond to theprecipitates X is preferably 10⁴ to 10⁸ per mm². This is because theaforementioned ranges provide particularly excellent bending property.If the number of precipitates is too small, the resultant alloy may nothave a targeted mechanical strength. On the other hand, if the number ofprecipitates is too large, the resultant alloy may be poor in bendingproperty. The number of precipitates X is more preferably 5×10⁹ to6×10¹¹ per mm², and the number of precipitates Y is more preferably 10⁴to 4×10⁷ per mm².

The effect of precipitates becomes remarkable as the amounts of Ni andSi are increased. A tensile strength of 800 MPa or more with the bendingproperty of R/t≦2.0, or a tensile strength of 700 MPa or more with thebending property of R/t≦1.0 may be attained, by controlling the numberof precipitates Y as described above. It is also possible to attain atensile strength of 800 MPa or more with the bending property ofR/t<1.5, or a tensile strength of 900 MPa or more with the bendingproperty of R/t<2. With respect to the stress relaxation resistance, thestress relaxation ratio of the copper alloy is preferably less than 20%,more preferably less than 18%, and further preferably 15% or less, inwhich an open-sided block method prescribed in the Standard of theElectronic Materials Manufacturers Association of Japan (EMAS-3003) isemployed with load stress set to be a surface maximum stress of80%-yield strength (80%-YS, 0.2%-proof stress), and the stressrelaxation ratio is measured under the conditions of at 150° C. for1,000 hours. The number of precipitates is represented by an averagenumber per unit area.

The copper alloy of the present invention may have a crystal graindiameter (i.e. an average of a minor axis diameter and a major axisdiameter) of generally 20 μm or less, preferably 10.0 μm or less. If thecrystal grain diameter is longer than 10.0 μm, it may be impossible toobtain a tensile strength of 720 MPa or more and a bending property ofR/t<2. More preferably, the crystal grain diameter of the copper alloyis 8.5 μm or less. The lower limit of the crystal grain diameter may begenerally 0.5 μm or more. The aforementioned crystal grain diameters aremeasured in the following manner: The crystal grain diameters aremeasured in two directions parallel to or perpendicular to the finallycold-rolled direction, respectively, on cross sections parallel to thedirection of thickness of the alloy sheet and parallel to the finallycold-rolled direction (the direction of the final plastic-working),thereby to determine larger lengths as major axis diameters and smallerlengths as minor axis diameters in respective directions. An averagevalue of each four lengths of the major axis diameters and minor axisdiameters is rounded up as a product of multiplying 0.005 mm times aninteger, to determine the crystal grain diameter.

Next, a specific example of a preferable production method for thecopper alloy according to the present invention involves: melting acopper alloy having the aforementioned preferable element composition;casting into an ingot; and hot-rolling the ingot. More specifically, theproduction method involves: heating the ingot at a temperature risingrate of 20 to 200° C./hr; holding the resultant ingot at 850 to 1,050°C. for 0.5 to 5 hours; hot-rolling; and, after finishing the hot-rollingat a finishing temperature of 300 to 700° C., quenching the hot-rolledproduct. In this way, the precipitate X, and the precipitate Ycorresponding to the element composition are formed. After hot-rolling,for example, the resultant alloy is formed into a given thickness,through a combination of solution treatment, annealing, andcold-rolling.

The purpose of the solution treatment is to allow Ni and Si precipitatedduring casting or hot-rolling, to form a solid solution again and torecrystallize at the same time. This permits the amount of the elementsin the solid solution to be increased and accumulated distortion duringworking to be removed, and a basic treatment for improving the strengthand bending property can be provided. The temperature of the solutiontreatment may be adjusted according to a Ni addition amount. Aspreferable embodiments, the solution treatment temperature is preferably600 to 820° C. for an Ni amount of 2.0 mass % or more but less than 2.5mass %, 700 to 870° C. for an Ni amount of 2.5 mass % or more but lessthan 3.0 mass %, 750 to 920° C. for an Ni amount of 3.0 mass % or morebut less than 3.5 mass %, 800 to 970° C. for an Ni amount of 3.5 mass %or more but less than 4.0 mass %, 850 to 1,020° C. for an Ni amount of4.0 mass % or more but less than 4.5 mass %, and 920 to 1,050° C. for anNi amount of from 4.5 mass % or more but less than 5.0 mass %. Sincecrystal grains are suppressed from being coarsened at high temperaturesin the alloy of the present invention to which the above-mentionedelements are added, the amount of elements in the solid solution isincreased by applying the solid solution treatment at highertemperatures, to thereby enable a high strength to be obtained.

For example, the heat treatment at 900° C. of an alloy material composedof N±3.0 mass % and S±0.7 mass %, allows sufficient Ni—Si precipitatesthat have already been precipitated, to form again the solid solution.However, the size of the crystal grain far exceeds 10 μm, and thebending property is conspicuously decreased. However, crystal grainswith a size of 10 μm or less may be obtained, even by a solid solutiontreatment at 900° C., from an alloy material to which any one of Cr, Co,Zr, and B is further added.

Further, for example, the heat treatment at 850° C. of an alloy materialwhose Ni content is 3.0 mass % and Si content is 0.7 mass %, allowssufficiently precipitated Ni and Si, to form again the solid solutionand thereby to give crystal grains of 10 μm or less. However, the heattreatment at the same temperature of an alloy having a too small Niamount causes growth of crystal grains into too large grains to therebyfail in obtaining a grain size of 10 μm or less. Further, on the otherhand, a too large Ni amount may not provide an ideal solution state, andthe mechanical strength may not be enhanced through the subsequent agingtreatment.

The size of the precipitate (e.g. precipitate Y) may be changed, bychanging the conditions of the solid solution treatment, i.e. byappropriately selecting the temperature of the solid solution treatment,as described above. For example, a higher temperature of the solidsolution treatment (a temperature higher by 50° C. than a standardtemperature) is selected for the heat treatment when the size ofprecipitate Y1 is to be increased, while a lower temperature of solidsolution treatment (a temperature lower by 50° C. than a standardtemperature) is selected for the heat treatment when the size ofprecipitate Y1 is to be decreased. In addition, the change of thedensity is coupled with the change of the crystal grain size, and thedensity becomes lower as the size is larger, while the density becomeshigher as the size is smaller.

The copper alloy of the present invention apparently providesimprovement in, in particular, bending property, and optionally stressrelaxation resistance, of a high strength copper alloy having a tensilestrength of 800 MPa or more, while high electrical conductivity ismaintained. Further, the copper alloy of the present invention providessimilar improvement in bending property of a copper alloy having atensile strength of less than 800 MPa. The copper alloy according to thepresent invention is also excellent in other properties, such as springproperty and the like.

EXAMPLES

The present invention will be described in more detail based on examplesgiven below, but the invention is not meant to be limited by these.

Example 1

An alloy component containing Ni, Si, Cr, and other elements in theamounts, as shown in Table 1, with the balance being Cu and inevitableimpurities, was melted with a high frequency melting furnace, and thethus-molten alloy was cast at a cooling rate from 10 to 30° C./second,to give an ingot with a size: thickness 30 mm, width 100 mm, and length150 mm. After holding the ingot at 900° C. for 1 hour, the resultantingot was subjected to hot-rolling, to give a hot-rolled sheet with asheet thickness (t) of 12 mm, each of the surfaces of the sheet waschamfered by 1 mm, to adjust the thickness (t) at 10 mm, and then thesheet was finished at a thickness (t) of 0.167 mm by cold-rolling. Thesheet material was then subjected to solid solution treatment. Thetemperature of the solid solution treatment was selected, in accordancewith the conditions described in the foregoing paragraph [0026]. Forchanging the size of precipitate Y1, a higher solid solution treatmenttemperature (a temperature higher by 50° C. than a standard temperature)was selected when the size of precipitate Y1 was to be increased, whilea lower solid solution temperature (a temperature lower by 50° C. than astandard temperature) was selected when the size of precipitate Y1 wasto be decreased, for conducting the heat treatment. The change of thedensity was coupled with the change of the crystal grain size, and thedensity became lower as the size was larger, while the density becamehigher as the size was smaller.

Immediately after the solution treatment, the sheet material wassubjected to water quenching. Then, each of the resultant alloys wassubjected to aging at a temperature of 450 to 500° C. for 2 hours andcold-rolling with a working ratio of 10%, to thereby obtain a sample oft=0.15 mm.

The following characteristics of the thus-obtained samples were testedand evaluated as mentioned in below, and the results are shown in Table2.

a. Electrical Conductivity (EC):

Electrical conductivity was calculated by measuring a specificresistance of the sample through a four terminal method in athermostatic bath maintained at 20° C. (±0.5° C.). The distance betweenthe terminals was set to 100 mm.

b. Tensile Strength (TS):

Tensile strengths of 3 test pieces prepared according to JIS Z 2201-13Bcut out from the sample in a direction parallel to the rollingdirection, were measured according to JIS Z 2241, and an average valuethereof was obtained.

c. Bending Property:

A test piece was cut out from the sample in a direction parallel to therolling direction into a size of width 10 mm and length 25 mm. Theresultant test piece was W-bent at 90° at a bending radius R that wouldbe 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.4, 0.5, or 0.6 (mm), with a bendingaxis being perpendicular to the rolling direction. Whether cracks wereoccurred or not at the bent portion, was observed with the naked eyethrough observation with an optical microscope of 50 timesmagnification, and the bent sites were observed with a scanning electronmicroscope to examine whether cracks were observed or not. Evaluationresults are designated by R/t (in which R represents a bending radius(mm), and t represents a sheet thickness (mm)), and the R/t wascalculated by employing a (limit) maximum R at which cracks wereoccurred. If no crack is formed at R=0.15 and cracks are formed atR=0.1, since the sample had a thickness (t)=0.15 mm, R/t=0.15/0.15=1 isobtained, which is shown in the following table. As the value of R/t issmaller, the bending property is improved.

d. Grain Size of Precipitate and Distribution Density:

The sample was punched out into a shape of a disc of diameter 3 mm, andthe resultant was subjected to thin-film-polishing by using a twinjetpolishing method. Photographs (5,000 and 100,000 times magnification) ofthe resultant sample were taken at 3 arbitrary positions with atransmission electron microscope at accelerating voltage 300 kV, and thegrain size of the precipitate and the density thereof were measured onthe photographs. Measurement of the grain size and density of theprecipitate were carried out in the following manner: setting anincident electron beam azimuth to [001], and measuring the number offine grains of the precipitate X composed of Ni—Si in a high-powerphotograph (100,000 times magnification) at n=100 (n represents thenumber of viewing fields for observation), since the precipitate X wasfine; and, on the other hand, measuring the number of grains of theprecipitate Y1 in a low-power photograph (5,000 times magnification) atn=10; thereby to eliminate the localized bias on the numbers. Thenumbers were calculated into numbers per unit area (/mm²).

e. Crystal Grain Diameter:

The crystal grain diameter was measured according to JIS H 0501 (cuttingmethod). The crystal grain diameters were measured in two directionsparallel to and perpendicular to the finally cold-rolled direction,respectively, on cross sections parallel to the direction of thicknessof the alloy sheet and parallel to the finally cold-rolled direction(the direction of the final plastic-working). The thus-measured lengthswere classified into larger lengths as major axis diameters and smallerlengths as minor axis diameters in respective directions. An averagevalue of each four lengths of the major axis diameters and minor axisdiameters was rounded up as a product of multiplying 0.005 mm times aninteger, to determine the crystal grain diameter.

TABLE 1 Ni Si Cr Other Classification No. [mass %] [mass %] [mass %][mass %] Example 1 2.31 0.52 0.08 — according to 2 3.22 0.73 0.62 — thisinvention 3 3.82 0.86 0.19 Zn: 0.51 4 4.22 0.95 0.22 Zn: 0.49 Sn: 0.15Mg: 0.11 5 4.81 1.09 0.41 Zn: 0.50 Sn: 0.12 Comparative 100 2.37 0.560.09 — example 101 3.35 0.80 0.13 — 102 3.94 0.94 0.19 Zn: 0.52 Sn: 0.15103 4.29 1.02 0.22 —

TABLE 2 Number Crystal Grain size of Grain size of of Y1/ grain Bendingprecipitate X precipitate Y1 number diameter TS EC propertyClassification No. [μm] [μm] of X [μm] [MPa] [% IACS] [R/t] Example 10.02 0.21 330 5 722 44 1.0 according to 2 0.03 0.19 430 6 764 40 1.0this invention 3 0.05 0.22 58 8 805 38 1.5 4 0.04 0.17 890 7 846 36 2.05 0.04 0.19 1020 5 887 33 2.0 Comparative 100 0.02 2.20 19 18 725 44 1.5example 101 0.03 0.001 16 22 764 41 2.5 102 0.03 0.004 18 19 803 39 3.0103 0.04 2.92 10 27 841 36 3.5

From the results shown in Tables 1 and 2, it is understood that thesamples according to the present invention have excellent properties inboth of the mechanical strength and the bending property. However, sincethe grain diameter of precipitate Y1 was outside of the range defined inthe present invention, the samples in Comparative examples 100, 101, 102and 103 each were poor in the bending property, as compared with thesamples in the examples according to the present invention having thesame level of mechanical strength, and the mechanical strength in thecomparative examples was not compatible to the bending property. Thus,it is possible to improve the bending property (R/t) while high strengthis maintained, by controlling the grain diameter of precipitate Y1 inthe Cu alloy system containing Ni, Si, and Cr. Based on the above, thecopper alloys of the examples according to the present invention can beconsidered to be favorable for materials of lead frames or the like.Further, the copper alloys of the examples according to the presentinvention are also excellent in other properties, such as springproperty.

Example 2

With respect to the copper alloys containing the elements in theamounts, as shown in Table 3, with the balance being made of Cu andinevitable impurities, the test was conducted in the same manner as inExample 1, except that the measurement was made on the precipitate Y2 inplace of the precipitate Y1. The results are shown in Table 4. Theproduction and measurement methods were also performed in the samemanner as in Example 1.

TABLE 3 Ni Si Co Other Classification No. [mass %] [mass %] [mass %][mass %] Example 6 2.33 0.48 0.09 — according to 7 3.20 0.67 0.55 — thisinvention 8 3.84 0.93 0.17 Zn: 0.51 9 4.29 1.02 0.14 Zn: 0.49 Sn: 0.15Mg: 0.12 10 4.82 1.09 0.37 Zn: 0.50 Sn: 0.12 Comparative 105 2.40 0.520.04 — example 106 3.26 0.77 0.19 — 107 3.94 0.86 0.19 Zn: 0.52 Sn: 0.15108 4.32 1.00 0.31 —

TABLE 4 Number Crystal Grain size of Grain size of of Y2/ grain Bendingprecipitate X precipitate Y2 number diameter TS EC propertyClassification No. [μm] [μm] of X [μm] [MPa] [% IACS] [R/t] Example 60.016 0.209 331 6 718 45 1.0 according to 7 0.021 0.189 442 6 759 40 1.0this invention 8 0.045 0.212 60 9 805 38 1.5 9 0.034 0.170 902 7 843 372.0 10 0.041 0.195 1035 5 877 34 2.0 Comparative 105 0.021 2.150 34 19723 44 1.5 example 106 0.031 0.009 19 22 763 41 2.5 107 0.029 0.005 1920 799 39 3.0 108 0.047 2.918 17 27 830 36 3.5

From the results shown in Tables 3 and 4, it is understood that thesamples according to the present invention have excellent properties inboth of the mechanical strength and the bending property. However, sincethe grain diameter of precipitate Y2 was outside of the range defined inthe present invention, the samples in Comparative examples 105, 106, 107and 108 each were poor in the bending property, as compared with thesamples in the examples according to the present invention having thesame level of mechanical strength, and the mechanical strength in thecomparative examples was not compatible to the bending property. Thus,it is possible to improve the bending property (R/t) while high strengthis maintained, by controlling the grain diameter of precipitate Y2 inthe Cu alloy system containing Ni, Si, and Co. Based on the above, thecopper alloys of the examples according to the present invention can beconsidered to be favorable for materials of lead frames or the like.Further, the copper alloys of the examples according to the presentinvention are also excellent in other properties, such as springproperty.

Example 3

With respect to the copper alloys containing the elements in theamounts, as shown in Table 5, with the balance being made of Cu andinevitable impurities, the test was conducted in the same manner as inExample 1, except that the measurement was made on the precipitate Y3 inplace of the precipitate Y1. The results are shown in Table 6. Theproduction and measurement methods were also performed in the samemanner as in Example 1.

TABLE 5 Ni Si Zr Other Classification No. [mass %] [mass %] [mass %][mass %] Example 11 2.42 0.59 0.07 — according to 12 3.18 0.84 0.69 —this invention 13 3.81 0.79 0.21 Zn: 0.51 14 4.31 1.01 0.30 Zn: 0.49 Sn:0.14 Mg: 0.10 15 4.77 1.08 0.36 Zn: 0.50 Sn: 0.13 Comparative 109 2.300.63 0.06 — example 110 3.28 0.83 0.15 — 111 3.90 0.78 0.20 Zn: 0.53 Sn:0.15 112 4.37 1.08 0.18 —

TABLE 6 Number Crystal Grain size of Grain size of of Y3/ grain Bendingprecipitate X precipitate Y3 number diameter TS EC propertyClassification No. [μm] [μm] of X [μm] [MPa] [% IACS] [R/t] Example 110.022 0.204 361 7 709 45 1.0 according to 12 0.021 0.195 448 7 747 421.0 this invention 13 0.050 0.225 80 9 802 39 1.5 14 0.035 0.174 916 8835 37 2.0 15 0.046 0.181 1048 5 875 33 2.0 Comparative 109 0.021 2.25043 19 715 45 1.5 example 110 0.031 0.009 19 23 751 42 2.5 111 0.0380.004 28 20 796 40 3.0 112 0.036 2.929 52 28 828 38 3.5

From the results shown in Tables 5 and 6, it is understood that thesamples according to the present invention have excellent properties inboth of the mechanical strength and the bending property. However, sincethe grain diameter of precipitate Y3 was outside of the range defined inthe present invention, the samples in Comparative examples 109, 110, 111and 112 each were poor in the bending property, as compared with thesamples in the examples according to the present invention having thesame level of mechanical strength, and the mechanical strength in thecomparative examples was not compatible to the bending property. Thus,it is possible to improve the bending property (R/t) while high strengthis maintained, by controlling the grain diameter of precipitate Y3 inthe Cu alloy system containing Ni, Si, and Zr. Based on the above, thecopper alloys of the examples according to the present invention can beconsidered to be favorable for materials of lead frames or the like.Further, the copper alloys of the examples according to the presentinvention are also excellent in other properties, such as springproperty.

Example 4

With respect to the copper alloys containing the elements in theamounts, as shown in Table 7, with the balance being made of Cu andinevitable impurities, the test was conducted in the same manner as inExample 1, except that the measurement was made on the precipitate Z inplace of the precipitate Y1. The results are shown in Table 8. Theproduction and measurement methods were also performed in the samemanner as in Example 1.

TABLE 7 Ni Si B Other Classification No. [mass %] [mass %] [mass %][mass %] Example 16 2.36 0.38 0.08 — according to 17 3.20 0.78 0.01 —this invention 18 3.87 0.86 0.10 Zn: 0.50 19 4.21 0.77 0.29 Zn: 0.49 Sn:0.15 Mg: 0.11 20 4.95 1.11 0.21 Zn: 0.48 Sn: 0.13 Comparative 113 2.440.59 0.21 — example 114 3.43 0.86 0.02 — 115 3.91 0.92 0.18 Zn: 0.50 Sn:0.15 116 4.31 0.89 0.08 —

TABLE 8 Number Crystal Grain size of Grain size of of Z/ grain Bendingprecipitate X precipitate Z number diameter TS EC propertyClassification No. [μm] [μm] of X [μm] [MPa] [% IACS] [R/t] Example 150.016 0.210 348 7 707 45 1.0 according to 16 0.023 0.187 441 8 743 411.0 this invention 17 0.044 0.232 106 9 802 39 1.5 18 0.036 0.170 921 9829 36 2.0 19 0.045 0.192 1054 6 870 34 2.0 Comparative 113 0.021 2.25059 20 712 46 1.5 example 114 0.030 0.007 42 23 750 43 2.5 115 0.0420.003 38 20 790 40 3.0 116 0.037 2.931 61 28 820 38 3.5

From the results shown in Tables 7 and 8, it is understood that thesamples according to the present invention have excellent properties inboth of the mechanical strength and the bending property. However, sincethe grain diameter of precipitate Z was outside of the range defined inthe present invention, the samples in Comparative examples 113, 114, 115and 116 each were poor in the bending property, as compared with thesamples in the examples according to the present invention having thesame level of mechanical strength, and the mechanical strength in thecomparative examples was not compatible to the bending property. Thus,it is possible to improve the bending property (R/t) while high strengthis maintained, by controlling the grain diameter of precipitate Z in theCu alloy containing Ni, Si, and B. Based on the above, the copper alloysof the examples according to the present invention can be considered tobe favorable for materials of lead frames or the like. Further, thecopper alloys of the examples according to the present invention arealso excellent in other properties, such as spring property.

Example 5

With respect to the copper alloys containing the elements in theamounts, as shown in Table 9, with the balance being made of Cu andinevitable impurities, the test was conducted in the same manner as inExample 1, except that the measurement was made on the precipitate Y2,Y3 or Z in place of a part of the precipitate Y1. The results are shownin Table 10. The production and measurement methods were also performedin the same manner as in Example 1.

TABLE 9 Cr, Co, Ni Si Zr, B Zn Sn Mg Classification No. [mass %] [mass%] [mass %] [mass %] [mass %] [mass %] Example 21 2.25 0.54 Cr: 0.08 0.20.10 0.20 according to 22 3.24 0.78 Co: 0.08 0.3 0.15 0.15 thisinvention 23 3.45 0.83 Cr: 0.2 0.5 0.10 0.10 Zr: 0.1 24 3.66 0.88 Zr:0.1 0.5 0.12 0.12 B: 0.02 25 3.87 0.93 Cr: 0.7 0.4 0.15 0.15 26 4.020.97 Cr: 0.2 0.2 0.18 0.11 Co: 0.1 27 4.27 1.02 Co: 0.8 0.5 0.22 0.21Zr: 0.1 28 4.48 1.07 Cr: 0.4 0.4 0.40 0.15 29 4.94 1.18 Cr: 0.3 0.5 0.320.14 Co: 0.1 Comparative 117 2.44 0.59 Cr: 0.09 0.4 0.25 0.12 example118 3.20 0.77 Co: 0.25 0.5 0.15 0.17 119 3.77 0.91 Zr: 0.2 0.2 0.20 0.09Cr: 0.1 120 3.94 0.95 Cr: 0.25 0.2 0.15 0.21 121 4.23 1.01 Cr: 0.3 0.30.12 0.14 Co: 0.1 122 4.70 1.13 Cr: 0.25 0.4 0.20 0.21

TABLE 10 Grain size of Crystal Grain size of precipitate Y1, Number ofY1, grain Bending precipitate X Y2, Y3, Z Y2, Y3, Z/ diameter TS ECproperty Classification No. [μm] [μm] number of X [μm] [MPa] [% IACS][R/t] Example 21 0.023 0.204 333 6 705 44 1.0 according to 22 0.0320.191 444 6 727 39 1.0 this invention 23 0.051 0.223 80 9 728 37 1.0 240.039 0.163 891 8 801 36 1.5 25 0.045 0.195 1031 5 809 34 1.5 26 0.0180.208 365 6 811 33 2.0 27 0.031 0.197 443 8 833 31 2.0 28 0.053 0.219 949 854 30 2.0 29 0.036 0.166 914 8 875 28 2.0 Comparative 117 0.021 2.27021 19 765 43 1.5 example 118 0.031 0.006 23 23 786 39 2.0 119 0.3042.103 26 23 807 35 2.5 120 0.044 0.001 28 20 828 33 3.0 121 0.032 0.00835 20 850 31 3.0 122 0.047 2.916 26 28 871 27 3.0

From the results shown in Tables 9 and 10, it is understood that thesamples according to the present invention have excellent properties inboth of the mechanical strength and the bending property. However, sincethe grain diameter of precipitate Y1, Y2, Y3 or Z was outside of therange defined in the present invention, the samples in Comparativeexamples 117, 118, 119, 120, 121 and 122 each were poor in the bendingproperty, as compared with the samples in the examples according to thepresent invention having the same level of mechanical strength, and themechanical strength in the comparative examples was not compatible tothe bending property. Thus, it is possible to improve the bendingproperty (R/t) while high strength is maintained, by controlling thegrain diameter of precipitate Y1 or the like. Based on the above, thecopper alloys of the examples according to the present invention can beconsidered to be favorable for materials of lead frames or the like.Further, the copper alloys of the examples according to the presentinvention are also excellent in other properties, such as springproperty.

In the following examples, it is shown that it is possible to controlthe stress relaxation resistance that has a large influence on thereliability particularly of connectors and terminal materials, bycontrolling the grain diameter of precipitate Y. While the copper alloysin the following examples according to the present invention areparticularly favorable as connectors and terminal materials, they arealso applicable to other uses, such as lead frame materials.

Example 6

With respect to the copper alloys containing Ni, Si, and elements in thegiven amounts as shown in Table 11, with the balance being made of Cuand inevitable impurities, the test was conducted in the same manner asin Example 1. The contents of Ni and Si were as follows: 3.5 mass % ofNi and 0.8 mass % of Si in the samples of Examples according to thepresent invention Nos. 1-4 and 1-11; 4.0 mass % of Ni and 0.95 mass % ofSi in the sample of Example according to the present invention No. 1-6;and 3.8 mass % of Ni and 0.86 mass % of Si in the samples of otherExamples according to the present invention and Comparative examples.The production and measurement methods for the samples were alsoperformed in the same manner as in Example 1. Further, the stressrelaxation resistance was evaluated by the following manner.

f. Stress Relaxation Resistance:

An open-sided block method prescribed in the Standard of the ElectronicMaterials Manufacturers Association of Japan (EMAS-3003) was employedwith load stress set to be a surface maximum stress of 80%-yieldstrength (80%-YS, 0.2%-proof stress), and the stress relaxation ratio(S.R.R.) was measured by placing the sample in a thermostat bath at 150°C. for 1,000 hours. When the stress relaxation ratio of the copper alloywas less than 20%, it is judged that the stress relaxation resistance is“good”, while when the S.R.R. was 20% or more, it is judged that thestress relaxation resistance is “poor”.

Herein, the terms ‘GW’ and ‘BW’ in the following tables are defined asfollows. GW denotes bending with a bend axis perpendicular to thedirection of rolling, by using a test piece sampled in parallel to thedirection of rolling; and BW denotes bending with a bend axis parallelto the direction of rolling, by using a test piece sampled perpendicularto the direction of rolling. In other words, GW means that thelongitudinal direction of the test piece is parallel to the direction ofrolling, and BW means that the longitudinal direction of the test pieceis perpendicular to the direction of rolling.

As is apparent from the results in Table 11, the samples according tothe present invention each have excellent properties with respect to themechanical strength, electrical conductivity, bending property, andstress relaxation resistance. In particular, it is possible to controlthe stress relaxation resistance by the grain size of precipitate Y, tomake the stress relaxation ratio be less than 20%. In the examplesaccording to the present invention, by making the grain size of Y withinthe range from 0.02 to 0.9 μm, it was possible to attain a good stressrelaxation ratio, which was a stress relaxation ratio of 13% or less,while maintaining excellent mechanical strength, electricalconductivity, and bending property. Based on the above, the alloys ofthe examples according to the present invention can be considered to befavorable, for example, for materials of terminals and connectors.Furthermore, although not shown in the examples, the similar effects canbe exhibited when the grain size of Y is within the range from 0.01 to2.0 μm. Contrary to the above, since the grain size of precipitate Y wastoo large due to a too large amount of B, the sample in Comparativeexample 1-1 was poor in the mechanical strength and the stressrelaxation resistance. Since the grain size of precipitate Y was toosmall due to a too small amount of Fe, the sample in Comparative example1-2 was poor in the stress relaxation resistance. Since the amount of Pwas too large, the sample in Comparative example 1-3 was poor in thestress relaxation resistance. Since the grain size of precipitate Y wastoo small, the sample in Comparative example 1-4 was poor in the bendingproperty and the stress relaxation resistance. Since the grain size ofprecipitate Y was too small, the sample in Comparative example 1-5 waspoor in the stress relaxation resistance. Since the grain size ofprecipitate Y was too small, the sample in Comparative example 1-6 waspoor in the stress relaxation resistance.

TABLE 11 Number Bending Component Precipitate X Precipitate Y of X/property α Size Density/ Composition Size Density/ number TS EC GW BWSRR mass % μm mm² Compound μm mm² of Y MPa % IACS R/t R/t % Thisinvention Cr = 0.2 0.03 3 × 10⁹ Ni—Si—Cr 0.2 2 × 10⁷ 150 862 36 1.0 1.09 1-1 This invention Cr = 0.1 0.03 8 × 10⁹ Ni—Si—Cr 0.3 6 × 10¹⁰ 0.1 85538 1.5 1.0 10 1-2 Zr = 0.1 Ni—Si—Zr Ni—Si—Cr—Zr This invention B = 0.0080.04 1 × 10¹⁰ Ni—Si—B 0.8 2 × 10⁹ 5 833 40 1.5 1.0 12 1-3 This inventionFe = 0.15 0.08 2 × 10⁷ Ni—Si—Fe 0.2 1 × 10⁵ 200 821 40 1.5 1.0 11 1-4 P= 0.09 Ni—Si—Fe—P This invention MM = 0.008 0.09 7 × 10⁷ Ni—Si-MM 0.5 3× 10⁶ 25 833 39 1.5 1.0 10 1-5 This invention Ti = 0.2 0.05 5 × 10⁹Ni—Si—Ti 0.2 2 × 10³ 250000 882 33 1.5 1.0 7 1-6 This invention O =0.006 0.04 3 × 10⁹ Ni—Si—O 0.8 7 × 10² 430000 832 37 1.5 1.0 11 1-7 Thisinvention Be = 0.01 0.05 6 × 10⁹ Ni—Si—Be 0.5 4 × 10⁷ 150 855 39 1.0 1.012 1-8 This invention Cr = 0.3 0.02 7 × 10¹⁰ Ni—Si—Cr 0.7 4 × 10⁸ 175852 37 1.0 1.0 11 1-9 Hf = 0.2 Ni—Si—Hf Ni—Si—Cr—Hf This invention C =0.009 0.09 3 × 10⁸ Ni—Si—C 0.5 3 × 10³ 10000 830 41 1.5 1.0 12 1-10 Thisinvention N = 0.01 0.07 2 × 10⁸ Ni—Si—N 0.9 5 × 10⁵ 400 820 38 1.0 1.012 1-11 This invention Mn = 0.2 0.08 4 × 10⁹ Ni—Si—Mn 0.5 5 × 10⁷ 80 84238 1.0 1.0 13 1-12 This invention In = 0.49 0.06 5 × 10⁹ Ni—Si—In 0.3 2× 10⁸ 25 845 36 1.0 1.0 12 1-13 Cr = 0.1 Ni—Si—Cr Ni—Si—In—Cr Thisinvention Al = 0.3 0.08 8 × 10⁸ Ni—Si—Al 0.02 2 × 10⁶ 400 839 37 1.0 1.010 1-14 This invention Co = 0.2 0.04 7 × 10⁹ Ni—Si—Co 0.7 4 × 10⁷ 175862 39 1.0 1.0 9 1-15 Comparative B = 1.1 1.25 2 × 10⁶ Ni—Si—B 2.2 2 ×10³ 1000 789 40 2.0 1.5 22 example 1-1 Comparative Fe = 0.002 0.04 3 ×10⁷ Ni—Si—Fe 0.005 3 × 10³ 10000 812 43 2.0 2.0 27 example 1-2Comparative P = 1.2 0.06 6 × 10⁹ Ni—Si—P 2.4 2 × 10³ 3000000 812 36 2.02.0 23 example 1-3 Comparative C = 0.005 0.03 4 × 10⁹ Ni—Si—C 0.007 1 ×10⁸ 40 845 39 2.5 2.0 28 example 1-4 Comparative Cr = 0.5 0.04 5 × 10⁹Ni—Ti—Cr 0.003 5 × 10⁹ 1 854 38 2.0 2.0 35 example 1-5 Comparative Be =0.05 0.03 7 × 10¹⁰ Ni—Ti—Be 0.007 6 × 10⁷ 1200 809 37 2.0 2.0 21 example1-6

Example 7

With respect to the copper alloys containing Ni, Si, and elements in thegiven amounts as shown in Table 12, with the balance being made of Cuand inevitable impurities, the test was conducted in the same manner asin Example 1. The contents of Ni and Si were as follows: 3.5 mass % ofNi and 0.8 mass % of Si in the samples of Examples according to thepresent invention Nos. 2-4 and 2-11; 4.0 mass % of Ni and 0.95 mass % ofSi in the sample of Example according to the present invention No. 2-2;and 3.8 mass % of Ni and 0.86 mass % of Si in the samples of otherExamples according to the present invention and Comparative examples.The production and measurement methods for the samples were alsoperformed in the same manner as in Example 1. Further, the stressrelaxation resistance was evaluated in the same manner as in Example 6.

As is apparent from the results in Table 12, the samples according tothe present invention each have excellent properties with respect to themechanical strength, electrical conductivity, bending property, andstress relaxation resistance. In particular, in the examples accordingto the present invention, by making the grain size of Y within the rangefrom 0.05 to 0.9 μm, it was possible to attain a stress relaxation ratioof 14% or less, while maintaining excellent mechanical strength,electrical conductivity, and bending property. Based on the above, thecopper alloys of the examples according to the present invention can beconsidered to be favorable, for example, for materials of terminals andconnectors. Further, the copper alloys of the examples according to thepresent invention are also excellent in other properties, such as springproperty. Contrary to the above, since the values of the precipitates Ywere outside of the range of from 0.01 to 2.0 μm, the samples inComparative examples each were poor in the stress relaxation ratio of21% or more.

TABLE 12 Number Bending Component Precipitate X Precipitate Y of X/property α β Size Density/ Composition Size Density/ number TS EC GW BWSRR mass % mass % μm mm² Compound μm mm² of Y MPa % IACS R/t R/t % Thisinvention Cr = 0.2 Ti = 0.01 0.04 2 × 10⁹ Ni—Cr—Ti 0.3 3 × 10⁷ 70 851 371.0 1.0 9 2-1 This invention Cr = 0.1 Zr = 0.2 0.02 4 × 10⁹ Ni—Cr—Zr 0.25 × 10¹⁰ 0.1 862 39 1.5 1.0 11 2-2 This invention B = 0.01 Mn = 0.020.05 2 × 10¹⁰ Ni—Mn—B 0.9 5 × 10⁹ 4 839 40 1.5 1.0 12 2-3 This inventionFe = 0.18 P = 0.09 0.07 5 × 10⁷ Ni—Fe—P 0.4 3 × 10⁵ 170 829 40 1.5 1.012 2-4 This invention MM = 0.008 O = 0.006 0.10 5 × 10⁷ Ni-MM-O 0.3 4 ×10⁶ 13 841 39 1.5 1.0 10 2-5 This invention Ti = 0.2 B = 0.02 0.04 6 ×10⁹ Ni—Ti—B 0.5 5 × 10³ 1200000 843 33 1.5 1.0 8 2-6 This invention O =0.004 Cr = 0.3 0.03 2 × 10⁹ Ni—Cr—O 0.3 2 × 10² 10000000 833 38 1.5 1.012 2-7 This invention Be = 0.02 Al = 0.02 0.06 7 × 10⁹ Ni—Be—Al 0.6 7 ×10⁷ 100 834 39 1.0 1.0 12 2-8 This invention Cr = 0.45 Hf = 0.1 0.03 8 ×10¹⁰ Ni—Cr—Hf 0.6 7 × 10⁸ 115 857 37 1.0 1.0 11 2-9 This invention C =0.009 Ti = 0.03 0.08 2 × 10⁸ Ni—Ti—C 0.6 3 × 10³ 67000 834 41 1.5 1.0 122-10 This invention N = 0.01 S = 0.006 0.08 7 × 10⁸ Ni—N—S 0.4 4 × 10⁵1750 825 39 1.0 1.0 12 2-11 This invention Mn = 0.2 Cr = 0.3 0.09 8 ×10⁹ Ni—Mn—Cr 0.6 7 × 10⁷ 115 846 40 1.0 1.0 14 2-12 This invention In =0.2 Cr = 0.5 0.09 9 × 10⁹ Ni—In—Cr 0.2 2 × 10⁸ 45 848 36 1.0 1.0 13 2-13This invention Al = 0.3 P = 0.03 0.03 6 × 10⁸ Ni—Al—P 0.05 3 × 10⁶ 200846 38 1.0 1.0 10 2-14 This invention Co = 0.2 Cr = 0.3 0.02 7 × 10⁸Ni—Co—Cr 0.30 7 × 10⁶ 100 859 38 1.0 1.0 11 2-15 Comparative B = 1.2 Mn= 0.19 2.25 6 × 10⁶ Ni—B—Mn 4.2 6 × 10³ 100 796 40 2.0 1.5 23 example2-1 Comparative Fe = 0.002 P = 0.001 0.09 6 × 10⁷ Ni—Fe—P 0.005 5 × 10³12000 816 43 2.0 2.0 27 example 2-2 Comparative P = 0.3 Fe = 0.4 0.03 9× 10⁹ Ni—Fe—P 3.3 3 × 10³ 3000000 815 36 2.0 2.0 23 example 2-3Comparative C = 0.05 Ti = 0.4 0.02 8 × 10⁹ Ni—C—Ti 0.005 3 × 10⁸ 25 85240 2.5 2.0 29 example 2-4 Comparative Cr = 0.45 P = 0.03 0.03 3 × 10⁹Ni—Cr—P 0.002 7 × 10⁹ 0.4 854 38 2.0 2.0 35 example 2-5 Comparative Zr =0.4 Fe = 0.2 0.07 8 × 10¹⁰ Ni—Fe—Zr 0.009 7 × 10⁷ 1150 813 36 2.0 2.0 21example 2-6

Example 8

With respect to the copper alloys containing Ni, Si, and elements in thegiven amounts as shown in Table 13, with the balance being made of Cuand inevitable impurities, the test was conducted in the same manner asin Example 1. The contents of Ni and Si were as follows: 3.5 mass % ofNi and 0.8 mass % of Si in the samples of Examples according to thepresent invention Nos. 3-4 and 3-11; 4.0 mass % of Ni and 0.95 mass % ofSi in the samples of Examples according to the present invention Nos.3-8 and 3-15; and 3.8 mass % of Ni and 0.86 mass % of Si in the samplesof other Examples according to the present invention and Comparativeexamples. The production and measurement methods for the samples werealso performed in the same manner as in Example 1. Further, the stressrelaxation resistance was evaluated in the same manner as in Example 6.

As is apparent from the results in Table 13, the samples according tothe present invention each have excellent properties with respect to themechanical strength, electrical conductivity, bending property, andstress relaxation resistance. In particular, in the examples accordingto the present invention, by making the grain size of Y within the rangefrom 0.2 to 0.6 μm, it was possible to attain a stress relaxation ratioof 15% or less, while maintaining excellent mechanical strength, bendingproperty, and electrical conductivity. Based on the above, the copperalloys of the examples according to the present invention can beconsidered to be favorable, for example, for materials of terminals andconnectors. Further, the copper alloys of the examples according to thepresent invention are also excellent in other properties, such as springproperty. Contrary to the above, since the values of the precipitates Ywere outside of the range of from 0.01 to 2.0 μm, the samples inComparative examples each were poor in the stress relaxation ratio of21% or more.

TABLE 13 Number Bending Component Precipitate X Precipitate Y of X/property α β Size Density/ Composition Size Density/ number TS EC GW BWSRR mass % mass % μm mm² Compound μm mm² of Y MPa % IACS R/t R/t % Thisinvention Cr = 0.45 Ti = 0.2 0.04 5 × 10⁹ Si—Cr—Ti 0.2 6 × 10⁷ 85 854 381.0 1.0 10 3-1 This invention Cr = 0.3 Zr = 0.15 0.01 2 × 10⁹ Si—Cr—Zr0.3 4 × 10¹⁰ 0.05 867 40 1.5 1.0 11 3-2 This invention B = 0.008 Mn =0.2 0.03 4 × 10¹⁰ Si—Mn—B 0.6 9 × 10⁹ 4 844 41 1.5 1.0 13 3-3 Thisinvention Fe = 0.28 P = 0.19 0.06 3 × 10⁷ Si—Fe—P 0.5 4 × 10⁵ 75 834 411.5 1.0 13 3-4 This invention MM = 0.005 O = 0.005 0.10 4 × 10⁷ Si-MM-O0.4 1 × 10⁶ 40 843 40 1.5 1.0 11 3-5 This invention Ti = 0.25 B = 0.030.03 3 × 10⁹ Si—Ti—B 0.2 9 × 10³ 330000 866 33 1.5 1.0 8 3-6 Thisinvention O = 0.004 Cr = 0.45 0.02 9 × 10⁹ Si—Cr—O 0.6 8 × 10² 11250000839 39 1.5 1.0 13 3-7 This invention Be = 0.008 Al = 0.012 0.02 5 × 10⁹Si—Be—Al 0.4 2 × 10⁷ 250 888 41 1.0 1.0 13 3-8 This invention Cr = 0.3Hf = 0.05 0.02 6 × 10¹⁰ Si—Cr—Hf 0.5 5 × 10⁸ 120 867 37 1.0 1.0 12 3-9This invention C = 0.01 Ti = 0.06 0.07 5 × 10⁸ Si—Ti—C 0.2 6 × 10³ 83000838 43 1.5 1.0 13 3-10 This invention N = 0.007 S = 0.008 0.05 9 × 10⁸Si—N—S 0.4 5 × 10⁵ 1800 828 39 1.0 1.0 12 3-11 This invention Mn = 0.25Cr = 0.5 0.04 8 × 10⁹ Si—Mn—Cr 0.3 2 × 10⁷ 400 848 40 1.0 1.0 15 3-12This invention In = 0.4 Cr = 0.3 0.09 6 × 10⁹ Si—In—Cr 0.2 2 × 10⁸ 30853 36 1.0 1.0 13 3-13 This invention Al = 0.1 P = 0.06 0.02 4 × 10⁸Si—Al—P 0.4 3 × 10⁶ 130 848 38 1.0 1.0 11 3-14 This invention Co = 0.2Cr = 0.15 0.03 3 × 10¹⁰ Si—Co—Cr 0.3 9 × 10⁸ 35 873 32 1.0 1.0 8 3-15Comparative B = 0.2 Mn = 0.5 0.37 9 × 10⁶ Si—B—Mn 3.2 8 × 10³ 1100 80541 2.0 1.5 23 example 3-1 Comparative Fe = 0.02 P = 0.008 0.07 3 × 10⁷Si—Fe—P 0.001 3 × 10³ 10000 818 44 2.0 2.0 28 example 3-2 Comparative P= 0.04 Fe = 0.1 0.01 1 × 10⁹ Si—Fe—P 3.3 6 × 10³ 170000 823 37 2.0 2.024 example 3-3 Comparative C = 0.005 Ti = 0.35 0.05 2 × 10⁹ Si—C—Ti0.005 1 × 10⁸ 20 856 41 2.5 2.0 29 example 3-4 Comparative Cr = 0.25 P =0.3 0.01 3 × 10⁹ Si—Cr—P 0.004 4 × 10⁹ 0.8 859 39 2.0 2.0 36 example 3-5Comparative Zr = 0.24 Fe = 0.12 0.06 4 × 10¹⁰ Si—Fe—Zr 0.005 2 × 10⁷2000 821 37 2.0 2.0 21 example 3-6

Example 9

With respect to the copper alloys containing Ni, Si, and elements in thegiven amounts as shown in Table 14, with the balance being made of Cuand inevitable impurities, the test was conducted in the same manner asin Example 1. The contents of Ni and Si were as follows: 3.5 mass % ofNi and 0.8 mass % of Si in the samples of Examples according to thepresent invention Nos. 4-1 and 4-4; 4.0 mass % of Ni and 0.95 mass % ofSi in the samples of Examples according to the present invention Nos.4-2 and 4-9; and 3.8 mass % of Ni and 0.86 mass % of Si in the samplesof other Examples according to the present invention and Comparativeexamples. The production and measurement methods for the samples werealso performed in the same manner as in Example 1. Further, the stressrelaxation resistance was evaluated in the same manner as in Example 6.

As is apparent from the results in Table 14, the samples according tothe present invention each have excellent properties with respect to themechanical strength, electrical conductivity, bending property, andstress relaxation resistance. In particular, in the examples accordingto the present invention, by making the grain size of Y within the rangefrom 0.1 to 0.6 μm, it was possible to attain a stress relaxation ratioof 15% or less, while maintaining excellent mechanical strength, bendingproperty, and electrical conductivity. Based on the above, the copperalloys of the examples according to the present invention can beconsidered to be favorable, for example, for materials of terminals andconnectors. Further, the copper alloys of the examples according to thepresent invention are also excellent in other properties, such as springproperty. Contrary to the above, since the values of the precipitates Ywere outside of the range of from 0.01 to 2.0 μm, the samples inComparative examples each were poor in the stress relaxation ratio of21% or more.

TABLE 14 Component Precipitate X Precipitate Y α β γ Size Density/Composition mass % mass % mass % μm mm² Compound This invention Cr = 0.5Ti = 0.1 Zr = 0.2 0.02 1 × 10⁹ Zr—Cr—Ti 4-1 This invention Cr = 0.25 Zr= 0.1 P = 0.05 0.02 5 × 10⁹ P—Cr—Zr 4-2 This invention B = 0.01 Mn =0.15 P = 0.2 0.06 9 × 10¹⁰ P—Mn—B 4-3 This invention MM = 0.005 O =0.005 S = 0.005 0.08 5 × 10⁷ MM-O—S 4-4 This invention Ti = 0.5 B =0.004 Cr = 0.3 0.05 4 × 10⁹ Cr—Ti—B 4-5 This invention O = 0.003 Cr =0.4 Zr = 0.12 0.20 3 × 10⁹ Zr—Cr—O 4-6 This invention B = 0.003 Al =0.01 Hf = 0.2 0.05 4 × 10⁹ Hf—Be—Al 4-7 This invention Cr = 0.2 Hf =0.15 Zr = 0.49 0.04 8 × 10¹⁰ Zr—Cr—Hf 4-8 This invention C = 0.03 Ti =0.08 S = 0.003 0.06 2 × 10⁸ Ti—C—S 4-9 This invention N = 0.008 S =0.008 O = 0.002 0.04 4 × 10⁸ O—N—S 4-10 This invention Mn = 0.5 Cr = 0.1Zr = 0.3 0.01 3 × 10⁹ Zr—Mn—Cr 4-11 This invention In = 0.3 Cr = 0.3 Zr= 0.3 0.03 8 × 10⁹ Zr—In—Cr 4-12 This invention Al = 0.25 P = 0.08 Ti =0.49 0.04 8 × 10⁸ Ti—Al—P 4-13 This invention Co = 0.1 Cr = 0.2 Zr = 0.30.03 3 × 10¹⁰ Co—Mn—Cr 4-14 Comparative B = 0.0002 Mn = 0.5 P = 0.6 0.554 × 10⁶ Mn—B—P example 4-1 Comparative C = 0.008 Ti = 0.2 Cr = 0.2 0.018 × 10⁹ Cr—C—Ti example 4-2 Comparative Cr = 0.25 P = 0.3 Al = 0.2 0.049 × 10⁹ Al—Cr—P example 4-3 Comparative Zr = 0.24 Fe = 0.12 S = 0.0030.02 5 × 10¹⁰ Fe—Zr—S example 4-4 Number Bending Precipitate Y of X/property Size Density/ number TS EC GW BW SRR μm mm² of Y MPa % IACS R/tR/t % This invention 0.1 1 × 10⁷ 100 822 39 1.0 1.0 10 4-1 Thisinvention 0.2 5 × 10¹⁰ 0.1 877 40 1.5 1.0 12 4-2 This invention 0.5 2 ×10⁹ 45 846 41 1.5 1.0 13 4-3 This invention 0.4 1 × 10⁶ 50 846 40 1.51.0 11 4-4 This invention 0.6 4 × 10³ 1000000 844 33 1.5 1.0 9 4-5 Thisinvention 0.5 3 × 10² 10000000 841 39 1.5 1.0 13 4-6 This invention 0.18 × 10⁷ 50 846 41 1.0 1.0 14 4-7 This invention 0.2 5 × 10⁸ 160 872 371.0 1.0 12 4-8 This invention 0.6 3 × 10³ 67000 847 43 1.5 1.0 13 4-9This invention 0.5 4 × 10⁵ 100 838 40 1.0 1.0 13 4-10 This invention 0.33 × 10⁷ 400 852 40 1.0 1.0 15 4-11 This invention 0.4 4 × 10⁸ 20 862 381.0 1.0 13 4-12 This invention 0.4 8 × 10⁶ 100 849 39 1.0 1.0 12 4-13This invention 0.3 1 × 10⁸ 300 852 40 1.0 1.0 15 4-14 Comparative 3.6 3× 10³ 130 807 42 2.0 1.5 24 example 4-1 Comparative 0.009 2 × 10⁸ 40 86041 2.5 2.0 30 example 4-2 Comparative 0.006 8 × 10⁹ 1.1 860 39 2.0 2.037 example 4-3 Comparative 0.004 5 × 10⁷ 1000 829 38 2.0 2.0 22 example4-4

INDUSTRIAL APPLICABILITY

The copper alloy of the present invention can be preferably applied, forexample, to lead frame, connector, or terminal materials for electricand electronic instrument materials, e.g. connector/terminal materials,relays, and switches for electric and electronic instruments, such ason-vehicle/automobile electric and electronic instruments.

Having described our invention as related to the present embodiments, itis our intention that the present invention not be limited by any of thedetails of the description, unless otherwise specified, but rather beconstrued broadly within its spirit and scope as set out in theaccompanying claims.

1. A method of producing a copper alloy, comprising the steps of:melting a copper alloy; casting into an ingot; heating the ingot at atemperature rising rate of 20 to 200° C./hr after said casting step;holding the resultant ingot at 850 to 1,050° C. for 0.5 to 5 hours;hot-rolling the ingot; and quenching the hot-rolled product, wherein,after said hot-rolling step, the resultant alloy is formed into a giventhickness, through a combination of solution treatment, annealing, andcold-rolling, wherein the solution treatment temperature is 600 to 820°C. for an Ni amount of 2.0 mass % or more but less than 2.5 mass %, 700to 870° C. for an Ni amount of 2.5 mass % or more but less than 3.0 mass%, 750 to 920° C. for an Ni amount of 3.0 mass % or more but less than3.5 mass %, 800 to 970° C. for an Ni amount of 3.5 mass % or more butless than 4.0 mass %, 850 to 1,020° C. for an Ni amount of 4.0 mass % ormore but less than 4.5 mass %, and 920 to 1,050° C. for an Ni amount offrom 4.5 mass % or more but less than 5.0 mass % and wherein the copperalloy has: a precipitate Y composed of Ni and/or Si and at least one ormore selected from the group consisting of B, Al, As, Hf, Zr, Cr, Ti, C,Fe, P, In, Sb, Mn, Ta, V, S, O, N, Misch metal (MM), Co, and Be; and aprecipitate X composed of Ni and Si, wherein a grain diameter of theprecipitate Y is 0.01 to 2 μm, and wherein the number of precipitates Xper mm² is 20 to 2,000 times the number of precipitates Y per mm².